Everything Before Us
by ashesandhoney
Summary: A TID AU in which Tessa was raised by Mortmain. "When a girl broke into the Institute in the middle of the night, Jem couldn't have guessed how completely she would change his life." Expect about 100k by the time it is is finished. (Rated M for language and violence)


Chapter 1: Enemy Inside the Gates

It was usually Will who roamed the halls in the dead of night but this evening it was him. Jem's joints had bothered him that day and he'd slept through the afternoon. Now it was well past midnight and he was wide awake so he took up Will's position as the ghost of the manor, drifting through the halls without a purpose. He was considering going back to his room to pull out his violin when he heard the sound of footsteps.

"Will?" he called out. The door to the spoils room was open which was rare itself. The only function of the 'historically relevant collection' that Jem had ever seen was for lessons with the tutor. Will hated the space and though it wasn't as gruesome as the collections in other Institutes, it wasn't Jem favourite place stepped into the doorway and there she was.

A girl.

She wore men's clothing that fit like it had been tailored to her but she was definitely a girl. She couldn't have been much more than 16. In the witchlight, her gray eyes were wide and her heavy braided coil of hair shone. Her eyebrows drew together in the faintest hint of confusion. Not alarm, not yet, maybe she thought he truly was a ghost with his strange colouring.

She stood in the center of the hallway, amid the dark wood and glass cases. Everything was ordered and cataloged and there were little plaques on each door to explain the contents. Someone, Jem didn't know who, had taken a tour around the British Museum and brought the systems there back. They had turned the spoils room into a sort of natural history gallery of Downworld.

"You're not Will. How did you get in here?" he asked her. Only a Shadowhunter could open the door of the Institute and with that thought he relaxed and smiled at her. She wore a long jacket and gloves so he couldn't see her runes but she must have come to the Institute for help and not rung the bell.

"Are you in danger? I can wake the Branwells, we can help or we can simply find you a room," he said stepping over to her. Her confusion deepened.

"You are Nephilim," she said, an educated British accent, he wondered which family she was from.

He held up his hand with the voyance rune and smiled again. Most people he spoke to knew the story, he wasn't used to having it be a surprise, "I am, my colouring is a little unusual but I am a Shadowhunter just as you are."

Comprehension dawned in her eyes, "You think I am Nephilim," she said.

"Aren't you?" he had gotten closer to her. What was she if she wasn't Nephilim? How had she gotten in? Perhaps she was a ghost. They rarely appeared in Institutes but it wasn't impossible. She looked solid enough but perhaps she was just a strong spirit.

"No," she said in that soft musical voice. There wasn't any hostility in it but Jem found himself drawing back and planning. She set him on edge. He had his cane if it came to a fight. He looked her over, she could be armed but not with long range weapons and she didn't stand like she was preparing for a fight.

"Why are you here?" he asked.

"I had been told that Nephilim keep the heads of warlocks on their walls," she said. Jem didn't bother to keep the little curl of disgust off his face. She wasn't wrong. He had seen it himself but it was one of the more disgusting habits he'd ever encountered. She looked back at the case she stood in front of. It was armour belonging to a Faerie warrior and it didn't hold her attention long.

"We don't, not here," he said and she looked at him with those serious, considering eyes. His anxiety was climbing. She looked so harmless and she spoke so calmly but she was an enemy inside the gates. Deep inside the gates. He needed to do something but until he knew what she was, he didn't want to raise an alarm and find himself in a battle he couldn't win. If he were honest, he didn't want to hurt her unless there was no other option.

"Most Nephilim just look like men, like any men on the streets, save the brands on their skin," she said. "Are you something different?"

"No," he said and he glanced around the room as unobtrusively as he could to see if they were truly alone. A bell sounded in the depths of the Institute beyond them and they both looked up. She was still not truly afraid, just curious and maybe a little wary.

"I need to leave now," she said.

"I don't think I can let you do that," he told her.

"Will you kill me?" she asked just as calmly as every other question. Jem's stomach turned because she wasn't just a girl, she couldn't be just a girl but she looked like one and he wanted to promise her that he wouldn't hurt her but he couldn't let her leave. He couldn't let something that had crept deep into the Institute in the middle of the night simply waltz back out.

"I don't want to," he said because it was true.

"I'm a warlock, you've killed others, I'm sure," she said.

"I haven't," he told her which was also true. He had killed things. He had killed demons. He had killed a vampire once but he had never killed a warlock. He'd barely even met any. He wondered how old she was, what her mark was, what her name was.

"If you need asylum, we can help you, I promise, no matter what you are," he said to her.

"But your father has, his father too, the Accords give it a veneer of civility but there is blood on your hands even if you didn't spill it. You are one of them," she said and she sounded sad. She looked so young standing there in that room like a child at lessons. He had stood there during lessons, right where she was now.

"Is that what this is about?" he asked, "Are you here to seek some revenge?"

"He calls it justice," she said.

"Who?" Jem asked.

"The Magister," she said. She spoke calmly and Jem was reminded again of a student, not because she was young but because it was a recitation. The words meant almost nothing to her. It was as though she said them because she had been told to, "You'll learn his name. He has a plan. Tonight was only the beginning. As you slay others, so shall you be slain. Your angel cannot protect you against that which neither God nor the devil has made, an army born neither of Heaven nor Hell."

He flicked the switch on the cane to release the blade though he didn't draw it yet. He was expecting her to run. He was prepared for her to try and fight but instead she melted. She vanished into her clothing as though she had shrunk. He stared at the pile of clothing puddled on the floor. Even her hair pins were still there, scattered about. He stepped a little closer and the bundle moved. His stomach churned again in some instinctive disgust.

Then a cat shot out.

It shot out and it ran towards the door but he was a Shadowhunter and he was faster than a cat. He slammed it shut and the cat careened away from him and took off down the alleys of cabinets. It was black and orange, a calico patchwork with long sleek fur. He stared after it.

"What the hell kind of magic is this?" he said to the empty room. It wasn't a glamour. It was a cat. She had changed form. She didn't appear to change form, she had actually done it. It wasn't like any kind of warlock magic he had ever heard of.

Jem crept towards the back of the room, looking for the animal that had been a girl. When he heard the door open he spun and ran for it. She must have doubled back and changed again but no, it was Will. He stood in the open door with his coat on and his black hair windblown from whatever escapade he had been on that night.

"Close the door," Jem called.

"Someone left the front door of the Institute open and you're concerned about this one?" Will asked standing in the open door and waving his hand at it like a tour guide. Jem had heard the ringing bell and he could hear footsteps now. The Institute was waking up.

"She's still in here, close the door, William," he said and Will did. He was about to make some sarcastic comment, Jem could see it on his face but at least he closed the damn door first.

"Who's still in here?" Will asked.

"The girl who seems to have walked into the Institute without setting off a single alarm, was sent by the Magister who, it turns out, has a plan and is now a cat," Jem said.

"Are you drunk?" Will asked.

"While that would make more sense, no I am not drunk. Are you?" Jem said trying to imagine how difficult it would be to manage a drunken Will on top of the girl.

"Not this evening. Is this girl naked?" Will asked with just the hint of a leer when he saw the pile of clothing.

"She's a cat. That wasn't a joke or a fancy metaphor from one of your novels. She turned into a cat and all her clothing fell off," Jem said again letting the exasperation into his voice.

Will had raised the alarm when he'd found the Institute doors open. Charlotte and Henry and all the servants were awake and hurrying about while they chased the cat who used to be a girl around the room. She was fast and small and human smart. They must have looked ridiculous trying to drop jackets on her and catch her in a corner.

Charlotte found them in the room with the cat closed up in an empty cabinet. Will sat in front of the door and glowered. His hand had been nearly shredded by her claws he'd pushed his jacket up to draw an iratze on his arm, muttering the entire time. The cat had hissed but now settled in and sat on her haunches from inside the glass case.

"The pyxis has been stolen while we all slept and the two of you are chasing your new pet around this ridiculous museum?" Charlotte said when she saw them. She wore a night dress and robe and her hair hung in two long plaits. She was small and thin and the hair style just made her look more like a child.

"She's a part of the team that stole it," Jem said while Will exploded and said loudly, "The pyxis is gone? That's impossible! Where was everyone?"

"She?" Charlotte asked ignoring Will's outburst. Jem had to tell the story again. The cat had bright green eyes but they had that same calm as the girl's gray ones had. The cat watched him more closely than she watched the others and he was reminded of her question about whether or not he would kill her. He wanted to reassure her but that was madness on a number of levels.

"So we've at least got a clue," Charlotte said looking at the cat who twitched her tail but didn't give any other evidence that she understood what was going on.

"We've got a hostile cat and a pile of clothing," Will said, "Which I suppose might be a clue if you squinted hard enough."

"I'm going to go call the Brothers, we'll see if we can get her returned to her natural form," Charlotte said, continuing to ignore Will's editorial, "I suppose I must also call the Clave."

"Well, this day is shaping up swimmingly and it isn't even dawn yet," Will said cheerfully and Jem kicked him in the ankle while he looked back at the cat who was still watching him with those too-intelligent eyes.


End file.
